This invention pertains to a batteryless fuel injection apparatus for a multi-cylinder internal combustion engine for driving an injector injecting a fuel into an intake pipe or a cylinder of a multi-cylinder internal combustion engine by an output of a generator driven by the engine without using any battery.
Such a fuel injection apparatus comprises an injector in the form of an electromagnetic fuel injection valve provided for each of the cylinders of the multi-cylinder internal combustion engine to inject the fuel into the intake pipe or the cylinder, a fuel pump to supply the fuel to the injector, an electric power circuit using an AC generator serving as an electric power source to generate a constant DC voltage, a signal generation device to generate pulse signals including a reference pulse signal for each of the cylinders which is generated at a reference rotational angle position set relative to each of the cylinders of the internal combustion engine and an electronic control unit (ECU) to receive an output of the signal generation device and outputs of various sensors such as a cooling water temperature sensor, an intake pipe internal pressure sensor, an air flow quantity sensor and so on serving to detect the conditions of the engine to control the injector for each of the cylinders using an output voltage of the electric power circuit as an electric power voltage.
The ECU generally comprises a microcomputer and includes cylinder judgment means to judge which cylinder each of the reference pulse signal generated by the signal generation device corresponds, injection quantity arithmetical operation means to arithmetically operate a fuel injection quantity from the injector for each of the cylinders using an rotation information of the engine obtained from the pulse signals generated by the signal generation device and various control conditions obtained from the various sensors, steady-state injection command generation means to generate an injection command signal for each of the cylinders having a signal width necessary for injecting the fuel from the injector for each of the cylinders in the injection quantity arithmetically operated by the injection quantity arithmetical operation means at the injection start position for each of the cylinders determined relative to the generation position of the reference pulse signal for each of the cylinders judged by the cylinder judgment means and an injector drive circuit to supply to the injector for each of the cylinders a drive current of valve-open level or higher using the output voltage of the electric power circuit as an electric power voltage while the injection command signal for each of the cylinders is generating.
The injector comprises a valve body having a fuel injection port at its leading end, a valve to open and close the fuel injection port of the valve body and an electromagnet for driving the valve body disposed within the valve body. The valve body is opened to inject the fuel while the drive current of valve-open level or higher is being supplied to the electromagnet.
The injector drive circuit to supply the drive current to the injector comprises a switch that gets an on-state while the injection command signal of rectangular waveform is being applied. The drive current flows from the electric power circuit through the switch to a drive coil for the injector.
Since a pressure of the fuel applied to the injector is normally kept constant by a pressure regulator, the injection quantity of the fuel from the injector is determined by the signal width of the injection command signal that corresponds to the fuel injection time.
In order to judge which cylinder each of a series of reference pulse signals generated by the signal generation device corresponds to, it is known that the signal generation device is adapted to generate a distinguishable cylinder judgment signal (a signal different from the reference pulse signals in its pulse width and its generation distance) which can be recognized by the ECU immediately before a reference rotational angle position of the specific cylinder (a rotational angle position of a crankshaft when a piston of the specific cylinder reaches the reference position for determining the ignition position and the fuel injection start position) to recognize that the reference pulse signal generated immediately after the cylinder judgment signal is detected is one corresponding to the specific cylinder or that a cylinder judgment signal generation device to generate a cylinder judgment signal (a signal generating once per one ignition cycle of the engine) is provided in addition to the signal generation device to generate the reference pulse signal to recognize that the reference pulse signal generated immediately after the cylinder judgment signal generation device generates the cylinder judgment signal corresponds to the specific cylinder.
Thus, it cannot be generally judged which the reference pulse signal corresponds to immediately after the starting operation begins when the engine should start, which will be referred to just as that the cylinder is judged later and the cylinder cannot be judged until the cylinder judgment signal is detected after the starting operation begins.
As aforementioned, the fuel injection apparatus for the multi-cylinder internal combustion engine is provided with the cylinder judgment means to judge which cylinder each of a series of the reference pulse signals generated by the signal generation device corresponds to determine the fuel injection start position of the injector for each of the cylinders based on the reference pulse signal for each of the cylinders judged by the cylinder judgment means. Thus, since the ECU cannot judge the cylinder for a while after the starting operation of the engine begins, the ECU simultaneously applies the injection command signals to all the injectors for the cylinders when each of the reference pulse signals is generated while the cylinders cannot be judged so that all the injectors for the cylinders simultaneously inject the fuel.
In case that the aforementioned fuel injection apparatus is used for a vehicle driven by the internal combustion engine and having no battery mounted thereon, the injector and the ECU are driven using a generator driven by the internal combustion engine as an electric power source.
As aforementioned, in some vehicle driven by the internal combustion engine having no battery mounted thereon, the injectors for all the cylinders are simultaneously operated when the engine starts. However, since the time for which the fuel is injected is so set longer as to improve the startability of the engine when it starts, the simultaneous operation of the injectors for all the cylinders tends to make the load of the generator excessive. In addition thereto, in the vehicle having no battery mounted thereon, since the engine is put into operation by human power using a recoil starter or a kick starter, the output voltage of the generator varies when the engine starts, which tends to cause the electric power voltage for the ECU or the injectors to be unstable. Thus, some internal combustion engine having the batteryless fuel injection apparatus used stops the operation of the ECU or repeat the stop of the operation and the resumption thereof due to the electric power voltage for the ECU lower than the minimum operation voltage therefor so that the injection of the fuel is not positively made and the engine fails to start. Even if the ECU can continue to be operated, the engine may be hard to start because the quantity of injection of the fuel is insufficient for the engine to start as the drive voltage of the injectors is lowered.
As the stop of the operation of the ECU and the resumption thereof are repeated when the engine starts, the simultaneous injection of the fuel into all the cylinders causes the fuel to be injected in the excessive amount, the ignition coils tend to be wet with the fuel, which sometimes disables the engine to start.
Especially, with the electrically driven fuel pump used for the fuel pump for supplying the fuel to the injectors, since the fuel pump acts as the load of the generator, the aforementioned problems further tend to arise.
Since the four cycle internal combustion engine has the large starter load and therefore the sufficiently higher rotational speed of the engine when it starts cannot be obtained, the output voltage of the generator tends to be short, which causes the aforementioned problems to arise in the same manner.
In order to prevent the aforementioned problems, it will be considered that the fuel begins to be injected by confirming that the relation of the correspondence of the cylinder to the reference pulse signal can be judged after the starting operation of the engine begins. In this case, since the start of the fuel injection is delayed, the amount of the fuel injection is short, which further disables the engine to start.
Accordingly, it is a principal object of the invention to provide a batteryless fuel injection apparatus for a multi-cylinder internal combustion engine adapted to improve the startability of the engine by preventing a drive voltage for an ECU and injectors from getting less than the minimum operation voltage thereof when the engine should start.
It is another object of the invention to provide a batteryless fuel injection apparatus for a multi-cylinder internal combustion engine adapted to improve the startability of the engine by positively injecting the fuel when the engine should start even though such a starter as used for a four cycle internal combustion engine has a large load so that a rotational speed of a generator cannot sufficiently increase.
In order to accomplish the object of the invention, the present invention provides a batteryless fuel injection apparatus for a multi-cylinder internal combustion engine comprising an injector provided for each of cylinders of the multi-cylinder internal combustion engine having n (n is an integer of 2 or more) cylinders to open a valve when a drive current of valve opening level or higher is applied to the valve to inject a fuel, a generator driven by the internal combustion engine, an electric power circuit to generate a predetermined DC voltage using the generator as an electric power source, a signal generation device to generate a reference pulse signal for each of the cylinders at a reference rotational angle position set relative to each of the cylinders, cylinder judgment means to judge which cylinder each of the reference pulse signals generated by the signal generation device corresponds to, injection quantity arithmetical operation means to arithmetically operate an injection quantity of the fuel from the injector for each of the cylinders using a rotation information obtained from the pulse signals generated by the signal generation device and control conditions obtained from various sensors, steady-state injection command generation means to generate an injection command signal for each of the cylinders having a signal width necessary for injecting the fuel from the injector for each of the cylinders in the injection quantity arithmetically operated by the injection quantity arithmetical operation means at the injection start position for each of the cylinders determined relative to the generation position of the reference pulse signal for each of the cylinders judged by the cylinder judgment means and an injector drive circuit to supply a drive current to the injector for each of the cylinders using the output voltage of the electric power circuit as an electric power voltage while the injection command signal for each of the cylinders is generating, the batteryless fuel injection apparatus further comprising start injection command generation means to generate a start injection command signal for each of the injectors or a start injection command signal common to m injectors (m is an integer of more than 1, but less than n) in predetermined provisional order to apply the start injection command signal to the injector drive circuit.
In general, as a crankshaft rotates for an angle corresponding to at least one ignition cycle after the starting operation of the engine begins, the judgment of the cylinders can be made. For instance, in case that a cylinder judging pulse is detected to judge the cylinders, as the crankshaft rotates for the angle corresponding to at least one ignition cycle, the cylinder judging pulses are always detected and therefore the cylinders can be judged. After the cylinders can be judged, the injection command signal generated by the steady-state injection command generation means is applied to the injector drive circuit whereby the injector for each of the cylinders can inject the fuel at the normal injection start position of the injector for each cylinder.
As aforementioned, after the starting operation of the engine begins and until the cylinder judgment means can judge the cylinders, as the start injection command signal for each of the cylinders or the start injection command signal common to one or more cylinders among the cylinders, but not all the cylinders is generated in provisional order to apply the start injection command signal to the injector drive circuit, even though the generator cannot generate enough output, all the injectors never serve as load of the generator simultaneously. This prevents the operation of the ECU from being unstably made due to the reduction of the output of the generator or stopping. Thus, because of the insufficient operation of the ECU due to the power voltage variation, there can be prevented from producing such troubles as the engine fails to start or is hard to start due to the ignition plug wet with the fuel.
The ECU determines the position of generation of the steady-state injection command signal on the position of generation of the reference pulse signal generated by the signal generation device. Thus, the start injection command generation means is preferably so constructed that the position of generation of the start injection command signal is determined by the reference pulse signal generated by the signal generation device.
With the fuel injected in provisional order immediately after the starting operation of the engine begins as aforementioned, when the fuel is injected at the normal fuel start position in accordance with the normal injection command signal generated by the steady-state injection command signal generation means after the cylinder can be judged, there possibly occurs an excess or a deficiency of the actual fuel injection quantity relative to the required injection quantity at any specific cylinder even though provisionally. In case that the excessive or deficient fuel injection quantity adversely affects the operation of the engine so that it cannot ignore, the correction of the excess or the deficiency should be made when the fuel is injected from the injector for each of the cylinders by the normal injection command signal.
To this end, there may be provided, for instance, start injection time storage means to store as a start injection time an accumulative value of injection time for which the fuel is injected by the injector for each of the cylinders in accordance with the start injection command signal and injection quantity correction means to judge the excess or the deficiency of the quantity of fuel already injected by the injector for each of the cylinders relative to the required quantity of fuel injection of each of the cylinders from the start injection time stored in the start injection time storage means when the injection command signal for each cylinder is switched from start injection command signal to the normal injection command signal generated by the steady-state injection command generation means and correct the signal width of the injection command signal generated by the steady-state injection command generation means so as to reduce the excess or the deficiency of the fuel quantity.
As the fuel quantity correction means is provided in this manner, the specific cylinder can be prevented from having the excessive or deficient fuel injection quantity when the engine should start and therefore the startability of the engine can be improved.
The correction of the injection quantity can be accomplished not only by the correction of the signal width, but also by stopping the normal injection command signal from being first generated by the steady-state injection command generation means in case that the excessive quantity of the fuel is already injected. More particularly, the injection quantity correction means may be so constructed as to correct the fuel injection quantity from the injector for each of the cylinders by controlling the normal injection command signal in such a manner as the signal width of the normal injection command signal first generated by the steady-state injection command generation means is narrowed or the first normal injection command signal stops from being generated in case that the quantity of the fuel already injected at each of the cylinders is more than the required injection quantity before the judgment of the cylinder finishes and the signal width of the normal injection command signal first generated by the steady-state injection command generation means is widened in case that the quantity of the fuel already injected to each of the cylinders is less than the required injection quantity.
In order to correct the excess or the deficiency of the fuel injection quantity, there may be provided, for instance, start injection frequency storage means to store the number of times of the fuel injection made by the injector for each of the cylinders in accordance with the start injection command signal and injection quantity correction means to judge the excess or the deficiency of the quantity of the fuel already injected by the injector for each of the cylinders relative to the required quantity of fuel injection of each of the cylinders from the number of times of fuel injection stored in the start injection frequency storage means when the injection command signal for each of the cylinders is switched from the start injection command signal to the normal injection command signal generated by the steady-state injection command generation means and correct the signal width of the injection command signal generated by the steady-state injection command generation means so as to reduce the excess or the deficiency of the fuel quantity.
In this case, the first normal injection command signal may also stop from being generated by the steady-state injection command generation means in case that the quantity of fuel already injected at each of the cylinders before the judgment of the cylinder finishes.
In case an electric pump is used as a pump to supply the fuel to the injectors, the electric pump also serves as loaded of the generator. In this case, since the fuel pump serves as big load of the generator, the generator tends to have excessive load if the injectors for all the cylinders are simultaneously driven and the power voltage of the ECU tends to be reduced.
Accordingly, the invention may be advantageously applied to the fuel injection apparatus in which the fuel pump serves as load of the generator in addition to the injectors.